This invention relates to a circuit arrangement for adjusting the amplitude of a signal, the arrangement comprising two differential transistor-amplifiers, one of said amplifiers being arranged to receive the signal via its main-current-path input and the other amplifier being arranged to receive a supply direct current corresponding to the d.c. component of the signal, the amplitude of the signal being adjustable by means of a control voltage applied to the cross-coupled control terminals of the differential amplifiers, and the signal whose amplitude has been adjusted being available on two cross-coupled main-current-path outputs.
Such a circuit arrangement is known from DE-PS 33 31 200. Said arrangement is used in an electronic potentiometer for adjusting the amplitude of the signal in dependence upon a control voltage. The signal is applied to the interconnected emitters constituting the signal input of a differential amplifier. The signal whose amplitude has been adjusted is available on two cross-coupled collecter terminals of the respective transistors of the differential amplifier. The coupled collecter terminals are further connected to a terminal of a voltage source via a load resistor, which voltage source supplies a supply voltage which is positive relative to ground potential. The signal whose amplitude has been adjusted is thus available in the form of a voltage across the load resistor.
In the known circuit arrangement the voltage representing the signal whose amplitude has been adjusted, the voltages across the differential amplifiers, and the voltage representing the input signal whose amplitude is to be adjusted, appear between the positive terminal of the voltage source and ground, i.e. the supply voltage should be at least equal to the sum of these three voltages.